When Perl is configured to use ithreads,
it will use re-entrant library calls in preference to non-re-entrant versions.
There is an incompatibility in OpenBSD's getprotobyname_r and getservbyname_r function in versions 3.7 and later that will cause a SEGV when called without doing a bzero on their return structs prior to calling these functions.
Current Perl's should handle this problem correctly.
Older threaded Perls (5.8.6 or earlier) will run into this problem.
If you want to run a threaded Perl on OpenBSD 3.7 or higher,
you will need to upgrade to at least Perl 5.8.7.